Loudspeaker and the like



30,1940. R GLEN 2,188,655

LOUD'SPEAKER AND THE LIKE Filed Sept. 50, 1937 INVENTOK M mm EMWW iii) Patented Jan. 30, 1940 UNITED STATES PATENT OFFICE LOUDSPEAKER AND THE LIKE Delaware Application September 30, 1937, Serial No. 166,534 In Great Britain October 6, 1936 8 Claims.

This invention consists of improvements in or relating to loudspeakers and the like. The object is to improve the tone quality of such sound reproducing devices. In the original production of complex sounds (for example in the playing of orchestral music) it is well known that sounds produced at any given instant, e. g. diiferent notes played simultaneously on diiferent instruments, do not necessarily affect the ear of a listener simultaneously and in other respects the aural perception of deep notes such as those of a drum differs widely from the aural perception of high notes such as those of a piccolo apart from the differences due to mere wave form as disclosed by an oscillograph. In relation to orchestral music for example such diiferences may be vaguely referred to as the orchestra] perspective and it is also well known that conductors take considerable trouble to arrange the groups of instruments in an orchestra to ensure a desired orchestral perspective.

It became clear to me from experience that many loudspeakers which were apparently reproducing the notes of different instruments reasonably well gave a total reproduction which lacked the perspective of the original production and a second object of this invention is to afford means for adjusting the reproduction of different groups of instruments so as to simulate the original perspective; and especially to obtain this result from a loudspeaker having a single drive or one integral diaphragm unit.

The use of a plurality of diaphragms is well known (e. g., tweeter cones and bass cones): these not only require separate electromagnetic drives and take up excessive space but they do not always achieve their object.

According to the present invention a diaphragm unit for a cone loudspeaker comprises a plurality of conical frusta together forming a single shell. These frusta may jointly form one cone. The different frusta may be from cones of different angles. The different frusta may be made of materials having different resonating capacities and the material of these frusta may vary in thickness as between different frusta.

In the case of a roughly conical diaphragm consisting of an apex portion and one or more adjoining frusta of cones united by an edge-toedge joint, the angles between the generating lines of the several conical surfaces employed may have different values varying between suitable limits, for example, between 156 and 194 degrees.

Other features of the invention will be apparent from the following description of preferred examples of the invention, made with reference to the accompanying drawing in which:

Figure 1 is a side sectional View of a cone loud speaker with a diaphragm unit constructed in accordance with the present invention,

Figure 2 is a side sectional view of the composite diaphragm embodying a modification oi the invention,

Figure 3 is an enlarged fragmentary View of part of the construction shown in Figure l, and

Figures 4, 5 and 6 are enlarged fragmentary sectional views of modifications of the invention.

Referring to Figure l, H denotes a framework for a loudspeaker which supports a diaphragm of the present invention consisting of two frusta 6 and I joined together and formed from cones of varying angles; each frustum being arranged to respond to a required range of frequencies and its resonating capacity is arranged accordingly.

In the modified construction shown in Figure 2, the tone properties of the diaphragm are varied by the provision of tapering pieces of material 8 embodied in or applied to the frusta 6 and 1 between the periphery and the apex of the diaphragm and formed from material of different resonating capacity from the remainder of the diaphragm.

It is a feature of the invention that the joints between the frusta shall be permanent and shall not injure the sound reproduction, and for this purpose the frusta are joined together with an adhesive, for example fish glue, to which a filler of powdered hard rubber has been added, which filler is indicated by dots, shown at 9 in Figures 3 and 4.

Figure 3 illustrates an example of the manner of forming a joint between two frusta in which the edges are made to abut and a bond of adhesive, as shown at 8, applied to the outer surface; the bonding agent comprising a glue containing the rubber filler. The adhesive so applied is preferably covered with a piece of adhesive tape l0. Where the frusta are of varying thicknesses the joint may be formed as shown in Figure 4, with a continuous interior surface.

Figure 5 illustrates another feature of the invention which consists in the provision of loading bands applied to the diaphragm to modify the tone quality of the loudspeaker. In Figure 5 the loading band I2 is arranged concentrically with the diaphragm and follows the line of the joint between the two frusta 6 and 1. The joint all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In loudspeakers and the like, a unitary'diaphragm of approximately conical form arranged to be driven electromagnetically and comprising frusta of at least two cones having different certral angles and disposed to form an edge-to-edge joint, and articulating means comprising a flexible band adhesively applied at one side to said frusta at the joint.

2. In loudspeakers and the like having'diaphragms oi the character set forth in claim 1 in which the articulating means comprises adhesive material and a band-like covering of adhesive tape encircles the diaphragm at the joint.

3. In loudspeakers and the like having diaphragms of the character set forth in claim 1 in which the applied adhesive consists of fish glue to which a filler of powdered hard rubber is added.

4. In loudspeakers and the'like having diaphragms of the character set forth in claim 1 in which loading materialis applied continuous ly atthe joint encircling the cone and adhesive- 1y retained.

5. In loudspeakers and the like having diaphragms of the character set forth in claim 1 in which loading is adhesively applied continuously at the joints and on therear surfaces of the frusta.

6. In loudspeakers and the like having diaphragms of the character set forth in claim 1 in which the loading is continuously applied and consists of tapered pieces of material applied to the frusta between the periphery and the apex of the diaphragm.

'7. In loudspeakers and the like having diaphragms of the character set forth in claim 1 in which the loading is continuously applied and consists of tapering strips of material of different resonating capacity from that of the frusta beingapplied to the surfaces of the frusta and loading bands are additionally applied along the edges of said tapering strips.

8. In loudspeakers and the like, a sound reproducing means adapted to be electromatically driven and comprising a cone adapted to be vibrated and an associated frustum supportedat its outer edge and joined to said cone its inner edge in a manner providing an edge-to-'edge joint, and flexible joining means comprising adhesive material including a loading agent and a covering of adh sive tape applied on one side at said joint ior uniting said frusturn' to said cone; said cone and irustuin subtending diilerent central angles.

ROBERT RODGER GLEN. 

